CVE-2026-93563

High CVSS 7.5

Published 2026-09-18 · last changed 2026-09-18

The fix

We hold no Microsoft remediation data for CVE-2026-93563, which normally means it is not a Windows CVE. For non-Microsoft software the fix is the vendor's own updated release, and the affected versions are listed below.

What it is

A flaw was found in Netty's `SmtpResponseDecoder` component. A remote attacker, acting as a malicious or man-in-the-middle (MITM) SMTP server, could exploit this by sending a specially crafted, unbounded multi-line SMTP response without a terminator. This vulnerability leads to unbounded memory accumulation within the client's Java Virtual Machine (JVM) heap, causing an `OutOfMemoryError` and a denial of service (DoS) due to a process crash.

Sources

NVD record for CVE-2026-93563

CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H